1. Field
One or more embodiments of the present invention relate to a secondary battery and a method of manufacturing the same, and more particularly, to a secondary battery on which a circuit protection element, such as a positive temperature coefficient (PTC) element, is attached, and a method of manufacturing the same.
2. Description of the Related Art
Secondary batteries are rechargeable and dischargeable batteries. Representative secondary batteries include a nickel-hydrogen battery, a lithium battery and a lithium ion battery. Secondary batteries are used in various products including portable electronic information devices such as mobile phones, notebook computers, electronic dictionaries, and electric devices such as electric bicycles, electric scooters and electric drills.
According to their shape, secondary batteries are divided into a cylindrical type, an oval type, a rectangular type, a square type and a pouch type.
In order to prevent damage and performance deterioration of a secondary battery due to overcharging and an overcurrent, the secondary battery may include a safety device such as a circuit protection module, a safety vent, a positive temperature coefficient (PTC) element, a thermal fuse, a separator, an additive or some combination thereof.
The PTC element increases its electrical resistance and thereby reduces current if a battery is heated above a certain temperature, thereby protecting the battery. Accordingly, the PTC element is not used in a battery that requires a high output in a harsh environment.
A high-capacity battery generally includes a PTC element for safety. Accordingly, a secondary battery including a PTC element may be appropriately used in products that are normally used in a mild environment and require safety rather than a high output, e.g., a notebook computer. On the other hand, a secondary battery not including a PTC element may be appropriately used in products that are normally used in a harsh environment and require a high output rather than safety, e.g., an electric bicycle, an electric scooter and an electric drill.
The resistance of a PTC element is determined according to the temperature of a battery and thus may be disposed at a position where the temperature is accurately sensed. Accordingly, it is more advantageous to include a PTC element in a battery as long as a space for the PTC element exists. A high-output/high-capacity secondary battery has a space for a PTC element and thus includes the PTC element inside.
In general, a high-capacity secondary battery for a notebook computer includes a PTC element inside while a medium-output or high-output secondary battery for a power tool, an electric bicycle, an electric scooter, a mower or a vacuum cleaner does not include a PTC element. As such, according to what the product that uses the secondary battery is, a high-capacity battery or a high-output battery has to be differently manufactured.